Strange result in 2 kinds of update

Hi,

I'm new to use MySQL with ASP.

Let say I've a table "Table1" and a column "col1" varchar(255)

Case 1 - if I use insert query like below is fine

insert into Table1(col1) values('abcdefghijk')

Case 2 - However, if I use the following code

with oRS
.AddNew
.Fields("col1") = "abcdefghijk"
.Update
end with

I'll get this error message

Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done.

In my experiance, this message say the field length is too short but in this case is not. Do any experts know this?

Urgent!

Jeff